1. Field of the Invention
The invention relates to a flexible heating element. More specifically, the invention relates to such a flexible heating element as either the type which can be used as the covering material for a heated chair or the type which can be disposed under the covering material, or the type which can be draped over an ordinary chair to transform it to a heated chair. The invention also relates to a dual proportional control means for controlling the power flow through the heating element.
2. Description of Prior Art
Heated chairs are known in the art as shown, for example, in the Volvo Brochure Parts Manual 1975. As will be appreciated, with heated chairs in a household, the ambient temperature of the house can be kept down since when a person is seated, he will be heated by the heated chair. When he is up and moving about, he does not require as much heat since his own body will be producing heat to warm him. Thus, the presence of heated chairs in a household can be energy conservative. Presently available heated chairs were provided for comfort only, and were therefore not designed to maximize energy conservation.
It is also known to provide flexible heating elements as described in U.S. Pat. No. 4,044,221, Kuhn, Aug. 23, 1977. However, this element of Kuhn is relatively bulky and is meant for installing in new seats. It can not be used as a covering material for a chair, or draped over an existing chair.
Heat responsive control circuits, for example, for electrically heated blankets, are also known in the art as described in Canadian Pat. Nos. 777,289, Wray, Jan. 30, 1968 and 868,615, Naoi et al, Apr. 13, 1971, as well as U.S. Pat. Nos. 3,422,244, Lauck, Jan. 14, 1969 and 3,564,203, Naoi et al, Feb. 16, 1971. The "General Electric SCR Manual, 4th Edition 1967" also illustrates a heat responsive control circuit on pages 186 to 189. However, none of these said heat responsive control circuits is a dual proportional control. None of these heat responsive controls can be variably set to regulate both (i) the firing angle of a triac determining the average power flowing through the load and (ii) the range of duty cycles (i.e. on off periods) dependent upon the rate of cooling determined by the ambient room temperature. None of these said heat responsive control circuits can provide the variety and degree of comfort control and saving of energy.